A 72-year-old Auschwitz survivor has taken his search for his twin brother to Facebook.

Menachem B., who wants to keep his last name private, last saw his brother 68 years ago when he was 4 years old. Menachem B.'s given name was Elias Gottesmann. He changed his name after surviving the concentration camp.

If his brother Jeno Gottesmann is alive, he could be anywhere with any name. The only definite link between the two is the "A7734" tattooed on their forearms from the concentration camp.

Memories from the time are few, but Menachem remembers that he had a twin brother. He also has a distinct memory of being outside playing in the yard and knowing his brother was asleep in bed when Nazi officers came to the house to take them. They lived in an area of Hungary that is now part of Ukraine.

Menachem, who now lives in Israel, recounted the memories to Ayana KimRon, the Israeli genealogist who is helping him look for his brother.

KimRon became involved in the case in May 2012, when she saw a posting on an online genealogical forum by one of Menachem's relatives. She was curious about the story and ended up speaking to Menachem.

"Meeting him face to face and seeing his reaction to the very little that I put in the conversation, I got hooked. I knew that if it's not me, nobody is going to do it," KimRon told ABCNews.com. "And then I got addicted, of course."

KimRon soon found out that Menachem and his brother Jeno, who went by the nickname Jolli, were transported to Auschwitz together in May 1944, a few months before their 4th birthdays.

Because they were twins, it is believed that they were subjected to "criminal medical experiments" that went on in Auschwitz laboratories, KimRon wrote on a Facebook page that she started for Menachem's search.

Records show that both brothers survived the war but were separated just days before liberation, according to KimRon. As the Germans fled Auschwitz, young Menachem found a man who was looking for his family and asked him to be his father.

In that moment, he made up a new name and told the man he didn't like the soldiers who hadn't saved his brother, he told KimRon. He moved to Israel with his new family and it was only later in life that his adoptive parents would tell him what he said about his brother, but he always had a feeling that his identical twin had survived.

"He sensed his brother, that he was alive somewhere," KimRon said.

"For the next 67 years he had a different name and no knowledge about his family," KimRon wrote on the Facebook page. "Now he knows. We also know that Jolli was very much alive at liberation. Maybe he too changed his name, maybe even changed his religion. The only definite link between them is the number tattooed on his arm -- A7734."

Menachem eventually reunited with some of his biological family, but has never stopped wanting to find his brother.

"I asked him, 'What are your expectations?' and he told me that he's trying to be practical and keep it very low," KimRon said. "He would be happy with Jolli's grandchildren."

"He may be concerned," she said. "The higher the expectation, the bigger the disappointment."

After months of research and dead ends, KimRon turned to Facebook for the world's help.

She posted a black and white photo of 5-year-old Menachem after the war and a photo of him now. The photo of him as a child has been shared more than 50,000 times and the Facebook page has more than 12,000 supporters from around the world.

KimRon said they have both been surprised and "overwhelmed" by the outpouring of support from around the world.

"In general, he feels lucky with the support and prayers and hope from all over the world," KimRon said. "I'm updating him at least once a day, if not twice."

KimRon said that the draw to Menachem and his story is stronger than just wanting to solve a mystery. She hopes helping him find his brother could "help him have a different state of mind and more emotional freedom in his life."

"It's a tough mission, but we'll get there," she said confidently.

"I gave him a promise," KimRon said. "I'm going to find his brother dead or alive, even if it takes me my whole life. I'm not going to stop."

Anyone with information about Jeno is asked to email FamilyRoots2000@gmail.com.